Biological sciences

Influence of different electron donors and acceptors on dehalorespiration of tetrachloroethene by Desulfitobacterium frappieri TCE1

Article Abstract:

The influence of varied electron donors/acceptors on dehalorespiration of tetrachloroethene by a novel dehalorespiring anaerobe, for which the name Desulfitobacterium frappieri TCE1 is proposed, is discussed. The bacterium is strictly anaerobic. A study was carried out to characterize the novel the dehalorespiring strain and to perform a detailed physiological study of its dehalorespiration. A comparative analysis of tetrachloroethene-dependent growth of the strain and dehalorespiration in some related Desulfitobacterium species was carried out. TCE1 is gram-positive, motile, and shaped like a curved rod with about 6 lateral flagella and is 2-4 by 0.6-0.8 micrometers.

A mathematical model of a mixed chemostat culture was constructed based on Michaelis-Menten-type kinetics for substrate utilization. The system consisted of an aerobic bacterium, Comamonas testosteroni, and an anaerobic bacterium, Veillonella alcalescens. Different kinetic parameters were obtained from oxygen-limited pure cultures. The model agreed well with mixed-culture observations. Increasing oxygen concentrations favored the aerobe and inhibited the anaerobe. Competition for common substrates showed the anaerobe to be the superior competitor. Among the growth parameters, response to oxygen was the most important factor determining coexistence.

Substrate uptake and utilization by a marine ultramicrobacterium

Article Abstract:

Examination of glucose uptake and alanine uptake and their utilization by a facultatively oligotrophic ultramicrobacterium reveals that the organism has an inherent property of mixed substrate utilization. The inducible glucose uptake system exhibits narrow substrate specificity, while broad substrate specificity is observed for alanine uptake system. Kinetic studies indicate the simultaneous utilization of glucose and alanine during growth in batch culture at high substrate levels and during substrate-limited growth in the chemostat.